1. Field of the Invention
The invention relates to a sheet feeding mechanism and related printer thereof, and more particularly, to a sheet feeding mechanism with duplex print function and related printer thereof.
2. Description of the Prior Art
In the prior art technology, when a user wishes to perform a printing operation on an unprinted side of a printing media the operation is performed with a single-sided media printer. Specifically, the printing media, having the unprinted side facing up, is fed by the user into the single-sided media printer so that printing on the unprinted side of the printing media can be performed. However, when a user wishes to perform printing on both sides of a printing media (i.e., double sided printing) the operation requires significant user intervention. Specifically, a printed side of the printing media must be reversed manually by the user so that an unprinted side of the printing media faces up. Thereby printing on the unprinted side of the printing media can be performed, and the requirement of printing on both sides (double sides) of the printing media is achieved. When the volume of the desired printing media to be generated in a double-sided fashion is smaller, the time consumed by the user for manually reversing a printed side of the printing media is acceptable. However, when the volume of printing media to be printed in a double-sided fashion is larger, the time consumed by the user for manually reversing a printed side of the printing media thereby performing double-sided printing increases significantly as compared to the time consumed for performing single-sided printing. Therefore, the inconvenient to the users is much greater.
The amount of time and the labor consumed by performing double-sided printing with single-sided media printers is inconvenient. Additionally, since the printing media is reversed manually while the single-sided media printer performing the double-sided printing, the unprinted second side of the printing media easily deviates from a designated position for printing. Therefore, the patterns of both sides of the printing media are inconsistent with each other. This results in the necessity of reprint the double-sided printing causing a waste in the consumed printing media.
In recent years, printers having duplex print function have gradually become the dominant product in the market. U.S. Pat. Nos. 6,185,381, 6,618,577, 4,806,979 disclose printers having duplex print function, which are typically accomplished by using discharge rollers to retract printing media in a reverse manner for performing the double sided printing. For instance, after one side of the printing media is printed, the printing media are retracted and another printing is performed on the unprinted side of the printing media. In other words, the printing performed on one printing medium must be completed before another printing is performed on the next printing medium, which ultimately decreases the overall printing speed and reduces the efficiency of the printer.